Power BI Interview Questions Asked at Confidential:

SQL Server:

1. Difference between RANK(), DENSE_RANK (), and ROW_NUMBER ()?

ROW_NUMBER () gives unique numbers with no ties.

RANK () adds gaps for ties.

DENSE_RANK () avoids gaps.

I use ROW_NUMBER () to pick top N rows, RANK () for actual ranking, and DENSE_RANK () for grouped categories.

2. Remove duplicates while keeping most recent record?

Use ROW_NUMBER () with PARTITION BY the key, order by date DESC, and pick row_num = 1 in a CTE.

6. Difference between inner query and correlated subquery?

Inner query runs independently. Correlated subquery runs row-by-row using outer query values—useful for comparisons like avg within group.

Power BI:

3. Handle inconsistent date formats in Excel or Power BI?

In Power BI, I use Power Query to convert text to date using Date.FromText() or locale settings. In Excel, I use TEXT, DATEVALUE, or Power Query.

4. Use of CALCULATE () in Power BI?

CALCULATE () changes the filter context of a measure. It's used to apply custom filters or perform time intelligence like YTD or previous month calculations.

5. Ensure data quality before delivering a report?

I check row counts, duplicates, nulls, apply sanity checks, cross-verify with source, and review filters/aggregations. A quick peer review helps too.

7. Column with 90% NULLs—what would you do?

If it’s not critical, I drop it. If useful, I impute or group it. But I always check the cause before deciding.

8. Stakeholder requests last-minute unrealistic change?

I acknowledge it, explain impact, suggest what’s doable within deadline, and push complex asks to next phase—clear communication is key.

9. Ways to reduce Power BI file size?

Remove unused columns, disable auto date, compress text, use aggregations, and consider incremental refresh.

10. How do you document logic behind KPIs and calculated fields?

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